Unblemished white teeth have long been considered cosmetically desirable. Unfortunately, in the absence of thorough dental cleaning, teeth can become discolored or stained from color-causing substances present in food, beverages, tobacco, and the like, and internal sources such as blood, amalgam-based fillings, and antibiotics (e.g., tetracycline).
Currently, there are a number of methods for removing stains in teeth. These methods are generally based on the use of abrasives, hydrolytic agents or oxidizing agents to break down the staining material. For example, mechanical methods of tooth cleaning are known whereby the stain is mechanically abraded through the use of abrasives or polishing agents normally employed in toothpaste preparations. Typical preparations containing abrasives are toothpastes, gels or powder dentifrices, which require close contact with the teeth. Typical abrasives include hydrated silica, calcium carbonate, sodium bicarbonate and alumina.
Hydrolytic agents, such as proteolytic enzymes, can also be used to whiten teeth. These products are usually in the form of pastes or gels, and function to whiten teeth by removing the plaque and calculus that have entrapped the stain.
Oxidizing agents such as urea peroxide, hydrogen peroxide or calcium peroxide, represent the most common forms of whitening agents for tooth enamels. It is believed that peroxides whiten teeth by releasing hydroxyl radicals capable of breaking down the plaque/stain complex into a form that can be flushed away or removed by an abrasive.
Other active stain-removing components include surface-active agents, such as anionic surfactants and chelators, which have been incorporated into stain-removing compositions because of their stain-removing properties. For example, anionic surfactants typically employed in dentifrice compositions include sodium lauryl sulfate and sodium N-lauryl sarcosinate. Furthermore, chelators, such as polyphosphates, are typically employed in dentifrice compositions as tartar control ingredients. For example, tetrasodium pyrophosphate and sodium tri-polyphosphate are typical ingredients found in such compositions.
Stain-removing gum compositions are known. For example, gum compositions including sodium tripolyphosphate and xylitol are known. Also, gum compositions are known, which include hexametaphosphate and an abrasive silica material. Moreover, a dental gum is known, which includes sodium tripolyphosphate, tetrasodium pyrophosphate, a silica abrasive and zinc acetate. A whitening gum composition is also known, which includes the abrasives sodium bicarbonate and calcium carbonate, and is sold under the brand name V6®.
Moreover, stain-removing gum compositions are known that include anionic surfactants such as fatty acid salts. For example, sodium stearate is a fatty acid salt employed in a gum product sold under the brand name Trident White® (see U.S. Pat. Nos. 6,471,945, 6,479,071 and 6,696,044). Furthermore, copending, commonly-owned U.S. patent application Ser. No. 10/901,511 discloses stain-removing gum compositions containing a salt of ricinoleic acid.
Current delivery systems for oral care/tooth whitening actives present problems. For example, the release of actives from tablets, films, mouthwashes, toothpastes and gels is quite rapid and occurs for a short period of time. Most of these products produce temporary, elevated levels of actives, followed by a rapid decrease to zero levels. Similarly, some tooth whitening actives can be released at elevated levels from gum bases within a few minutes following mastication, followed by a rapid decrease to low levels.
Encapsulating materials have been used previously to encapsulate sweeteners, acids, flavorings, soluble dietary fibers, biologically active agents, breath freshening agents, and the like. Such encapsulating materials have included, for example, cellulose and its derivatives, arabinogalactin, gum arabic, polyolefins, waxes, vinyl polymers, gelatin and zein. In general, encapsulating actives in edible compositions has been used to slow their degradation, to enhance the uniformity of their release, and to prolong their release in a controlled manner.
The selection of a suitable encapsulating material (e.g., polyvinyl acetate, PVAc) has usually been focused on the molecular weight of the encapsulating material, with higher molecular weights generally associated with longer release times. However, this approach is limited in that a predictable modification of the release profile of an active is made only through the modification of the molecular weight of the encapsulating material.
In view of the foregoing, it would be beneficial to provide oral delivery systems wherein a controlled amount of an oral care active is delivered to an oral cavity over a longer period of time, rather than delivering a high concentration of the active followed by no active. In particular, it would be advantageous to encapsulate at least one oral care active in a suitable polymer matrix to enhance the uniformity of its release, and to prolong its release in a controlled manner. In some embodiments, the release profile of the active may be modified by selection of a polymer matrix having a tensile strength within a desirable range and/or may be modified by including in the matrix a polymer having a water absorption within a desirable range.